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Merge pull request #34667 from rpigott/resolved-bypass

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resolve: fixes for sd-resolved bypass
This commit is contained in:
Lennart Poettering 2024-10-21 12:34:24 +02:00 committed by GitHub
commit 069da86dbc
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GPG Key ID: B5690EEEBB952194
4 changed files with 25 additions and 13 deletions
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1
src/resolve/resolved-dns-packet.h
View File

@ -111,6 +111,7 @@ static inline uint8_t* DNS_PACKET_DATA(const DnsPacket *p) {
#define DNS_PACKET_AD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 5) & 1)
#define DNS_PACKET_CD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 4) & 1)
#define DNS_PACKET_FLAG_CD (UINT16_C(1) << 4)
#define DNS_PACKET_FLAG_AD (UINT16_C(1) << 5)
#define DNS_PACKET_FLAG_TC (UINT16_C(1) << 9)

20
src/resolve/resolved-dns-stub.c
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@ -462,10 +462,6 @@ static int dns_stub_finish_reply_packet(
rcode = DNS_RCODE_SERVFAIL;
}
/* Don't set the CD bit unless DO is on, too */
if (!edns0_do)
cd = false;
/* Note that we allow the AD bit to be set even if client didn't signal DO, as per RFC 6840, section
* 5.7 */
@ -631,7 +627,7 @@ static int dns_stub_send_reply(
!!q->request_packet->opt,
edns0_do,
(DNS_PACKET_AD(q->request_packet) || DNS_PACKET_DO(q->request_packet)) && dns_query_fully_authenticated(q),
DNS_PACKET_CD(q->request_packet),
FLAGS_SET(q->flags, SD_RESOLVED_NO_VALIDATE),
q->stub_listener_extra ? ADVERTISE_EXTRA_DATAGRAM_SIZE_MAX : ADVERTISE_DATAGRAM_SIZE_MAX,
dns_packet_has_nsid_request(q->request_packet) > 0 && !q->stub_listener_extra);
if (r < 0)
@ -686,6 +682,7 @@ static int dns_stub_patch_bypass_reply_packet(
DnsPacket **ret, /* Where to place the patched packet */
DnsPacket *original, /* The packet to patch */
DnsPacket *request, /* The packet the patched packet shall look like a reply to */
bool validated,
bool authenticated) {
_cleanup_(dns_packet_unrefp) DnsPacket *c = NULL;
int r;
@ -726,9 +723,14 @@ static int dns_stub_patch_bypass_reply_packet(
DNS_PACKET_HEADER(c)->flags = htobe16(be16toh(DNS_PACKET_HEADER(c)->flags) | DNS_PACKET_FLAG_TC);
}
/* Patch the cd bit to reflect the state of validation: set when both we and the upstream
* resolver have checking disabled. */
DNS_PACKET_HEADER(c)->flags = htobe16(UPDATE_FLAG(be16toh(DNS_PACKET_HEADER(c)->flags),
DNS_PACKET_FLAG_CD, DNS_PACKET_CD(original) && !validated));
/* Ensure we don't pass along an untrusted ad flag for bypass packets */
if (!authenticated)
DNS_PACKET_HEADER(c)->flags = htobe16(be16toh(DNS_PACKET_HEADER(c)->flags) & ~DNS_PACKET_FLAG_AD);
DNS_PACKET_HEADER(c)->flags = htobe16(UPDATE_FLAG(be16toh(DNS_PACKET_HEADER(c)->flags),
DNS_PACKET_FLAG_AD, authenticated));
*ret = TAKE_PTR(c);
return 0;
@ -751,6 +753,7 @@ static void dns_stub_query_complete(DnsQuery *query) {
_cleanup_(dns_packet_unrefp) DnsPacket *reply = NULL;
r = dns_stub_patch_bypass_reply_packet(&reply, q->answer_full_packet, q->request_packet,
/* validated = */ !FLAGS_SET(q->flags, SD_RESOLVED_NO_VALIDATE),
FLAGS_SET(q->answer_query_flags, SD_RESOLVED_AUTHENTICATED));
if (r < 0)
log_debug_errno(r, "Failed to patch bypass reply packet: %m");
@ -982,7 +985,7 @@ static void dns_stub_process_query(Manager *m, DnsStubListenerExtra *l, DnsStrea
protocol_flags|
SD_RESOLVED_NO_CNAME|
SD_RESOLVED_NO_SEARCH|
SD_RESOLVED_NO_VALIDATE|
(DNS_PACKET_CD(p) ? SD_RESOLVED_NO_VALIDATE | SD_RESOLVED_NO_CACHE : 0)|
SD_RESOLVED_REQUIRE_PRIMARY|
SD_RESOLVED_CLAMP_TTL|
SD_RESOLVED_RELAX_SINGLE_LABEL);
@ -990,6 +993,7 @@ static void dns_stub_process_query(Manager *m, DnsStubListenerExtra *l, DnsStrea
r = dns_query_new(m, &q, p->question, p->question, NULL, 0,
protocol_flags|
SD_RESOLVED_NO_SEARCH|
(DNS_PACKET_CD(p) ? SD_RESOLVED_NO_VALIDATE | SD_RESOLVED_NO_CACHE : 0)|
(DNS_PACKET_DO(p) ? SD_RESOLVED_REQUIRE_PRIMARY : 0)|
SD_RESOLVED_CLAMP_TTL);
if (r < 0) {

6
src/resolve/resolved-dns-transaction.c
View File

@ -840,10 +840,8 @@ static void dns_transaction_cache_answer(DnsTransaction *t) {
dns_transaction_key(t),
t->answer_rcode,
t->answer,
DNS_PACKET_CD(t->received) ? t->received : NULL, /* only cache full packets with CD on,
* since our use case for caching them
* is "bypass" mode which is only
* enabled for CD packets. */
/* If neither DO nor EDE is set, the full packet isn't useful to cache */
DNS_PACKET_DO(t->received) || t->answer_ede_rcode > 0 || t->answer_ede_msg ? t->received : NULL,
t->answer_query_flags,
t->answer_dnssec_result,
t->answer_nsec_ttl,

11
test/units/TEST-75-RESOLVED.sh
View File

@ -517,8 +517,17 @@ testcase_08_resolved() {
grep -qF "fd00:dead:beef:cafe::11" "$RUN_OUT"
grep -qF "authenticated: yes" "$RUN_OUT"
run dig +short signed.test
run dig +nostats signed.test
grep -qF "10.0.0.10" "$RUN_OUT"
grep -q "flags:[^;]* ad" "$RUN_OUT"
run dig +nostats +cd signed.test
grep -qF "10.0.0.10" "$RUN_OUT"
grep -q "flags:[^;]* cd" "$RUN_OUT"
grep -qv "flags:[^;]* ad" "$RUN_OUT"
run dig +nostats +do signed.test
grep -qF "10.0.0.10" "$RUN_OUT"
grep -q "flags:[^;]* ad" "$RUN_OUT"
grep -qv "flags:[^;]* cd" "$RUN_OUT"
run resolvectl query signed.test
grep -qF "signed.test: 10.0.0.10" "$RUN_OUT"
grep -qF "authenticated: yes" "$RUN_OUT"